If five times the fifth term of an AP is equal to seven

If five times the fifth term of an AP is equal to seven times the seventh term of the AP, then what is the twelfth term ?

T₅ = a + 4d, T₇ = a + 6d
∴ 5(a + 4d) = 7(a + 6d)
⇒ 5a + 20d = 7a + 42d
⇒ a = -11d
⇒ T₁₂ = a + 11d = - 11d + 11d = 0
So, the twelfth term is 0.